Compared with a CRT (Cathode Ray Tube), a liquid crystal display device has advantages of a thin and lightweight body, and low power consumption with a low driving voltage. For this reason, the liquid crystal display device has been conventionally adopted in various electronic devices, such as a television, a laptop PC (Personal Computer), a desktop PC, a PDA (Personal Digital Assistant: mobile terminal), and a mobile phone.
Particularly, a liquid crystal display device (TFT liquid crystal display device) employing a TFT (Thin Film Transistor) element realizes high display quality by switching each pixel via a TFT element.
Meanwhile, as it becomes rapidly popular that a television receiver or the like employs a liquid crystal display device to display moving images, it is required to cause a liquid crystal display panel of the liquid crystal display device to have higher response speed in order to display moving images with high quality.
A liquid crystal display device employing an OCB mode has recently drawn attention. The OCB mode liquid crystal display device (OCB panel) generally has such an arrangement that (i) liquid crystal molecules are sandwiched between two substrates which were subjected to alignment treatment, so that the liquid crystal molecules are aligned parallel to each other in the same direction, (ii) a wave plate is stacked to a surface of each of the substrates, and further, (iii) a polarizer is stacked to each of the substrates so that transmission axes of the polarizers have a cross nicol relationship.
(Reverse Transition)
In a case where the aforementioned OCB liquid crystal display device is used in a normally-white mode (NW mode), which caries out (i) black display while a high voltage is being applied, and (ii) white display while a low voltage is being applied, for example, it is necessary to reduce a voltage applied to a liquid crystal layer down to about a critical voltage (Vcr) between a spray orientation and a bend orientation so as to realize the white display having a high transmissivity.
This causes, in some cases, a bend-spray transition (reverse transition), which is a phenomenon where liquid crystal molecules that have had the bend orientation have the spray orientation again, thereby causing a defect in a displayed image.
(High White Voltage)
In order to inhibit such a reverse transition, various methods have been proposed. For example, there has been proposed a method of causing a voltage (white voltage) applied during the white display in the normally-white mode to be sufficiently higher than the critical voltage (Vcr).
However, in this method of increasing the white voltage, since there is a trade-off relationship between the increase in white voltage, and a luminance (as illustrated in FIG. 17), it is difficult to realize an OCB panel having a high luminance.
FIG. 17 is a view showing a relationship between the applied voltage and a transmissivity in an OCB mode liquid crystal display device (normally-white mode). The “Vcr” is a critical voltage between the spray orientation and the bend orientation.
(Black Insertion)
Further, there is another method to prevent the reverse transition, in which other than an image signal, a signal for inhibiting such a reverse transition phenomenon is supplied (see Patent Literature 1).
Specifically, there has been proposed a method of stably maintaining the bend orientation by inserting the black display once or more within one frame of image display, for example.